<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        你真是个天才
    </div>

</body>
</html>
<script src="./jquery.js"></script>
<script>
    var tools= function(){
        var app = document.getElementById('#app')
            var setColor = function(){
                this.app.style.color = "red"
                var setFontSize = function(){
                this.app.style.fontSize ="30px"
                this.app.onclick = alert("你呀总能给我整点花样")
                   
            }
            setFontSize();
            }
            setColor();
            
    }
        tools();
</script>